Tissue engineering aims at restoring, maintaining or improving tissue function so as to extend and/or preserve the well being of an individual while decreasing the major cost burden on the medical community. These natural processes are occurring in nature using the 3D-structure of extracellular matrix (ECM) (the natural scaffold), which allows cells to grow, proliferate and differentiate within it. Artificial scaffolds have been made and used for therapeutic purposes (i.e. cardiac or skin implants) from natural polymers that desorb or degrade within the body.
The major challenge for tissue engineering researchers is to find materials and processing techniques that allow them to produce ECM mimicking scaffolds that promote cell growth and organization into a specific architecture, inducing differentiated cell function. ECM is a complex three-dimensional ultrastructure of proteins, proteoglycans and glycoproteins, used for cells growth in native tissue. In fact, there are many different types of ECMs for different parts of the body, for example, fibrous proteins are dominant material in tendon, polysaccharides are found largely existing in cartilage and so the forth. Collagens have been found to be the key proteins in ECM and also are the most ample proteins in the whole body.
ECM provides attachment sites and mechanical support for cells. The topology of ECM has been found to affect the cell structure, functionality and its physiological responsiveness. The geometry of the natural matrix was reported to modulate the cell polarity. Thyroid cells, smooth muscle cell and hepatocytes are different types of cells found to be affected by ECM's topology, with 3D-structures inducing cell differentiation more effectively than 2D configurations. The arrangement of ECM's configuration involves multiple length scales, layers and morphologies. However, although much is know about 3-D scaffolding of materials according to ECM topology to proliferate cell growth, satisfactory techniques and/or synthetic scaffolds have not been easily to construct.
In human skin, dermal fibroblasts secrete keratinocyte growth factor (KGF) and other growth factors that regulate keratinocyte proliferation and migration (Huang, et al., 2005, J Biomed Sci. 12(6): 855-67), while keratinocyte-derived cytokines may downregulate collagen synthesis by fibroblasts (Harrison, et al., 2006, Br J Dermatol. 154(3): 401-10). In large or non-healing wounds, this epithelial-mesenchymal interaction is obstructed by the lack of physical and biochemical cues for host cells to migrate and repair the wound site. Hence, an implantable platform is needed to provide an environment inductive to skin regeneration, by recruiting host cells and inducing them to secrete the appropriate signals and matrix components for repair.
Accordingly, there is a need for bioengineered tissue substitutes that can be custom-engineered to match the biomechanical, biochemical, and biological needs of the specific tissue or organ they are designed to replace.